A known liquid measuring and dispensing device comprises a flow tube providing inflow and outflow ducts, the inflow duct having an inflow part in the tube sidewall, a measuring chamber embracing the flow tube and having a cylindrical inside wall member axially slidable along the outer surface of the flow tube and provided with liquid seals adjacent its ends, and upper and lower further ports in the chamber inside wall. Means are provided in the tube to prevent direct flow of liquid through the tube between the inflow and outflow ducts. The chamber is slideable between an upper position and a lower position. In the lower position, the upper further port is in the register with the inflow port and the lower further port is out of register with the inflow port whereby the chamber can be filled from the inflow duct. In the upper position, the upper further port is out of register with the inflow port and the lower further port is in register with the inflow duct whereby the chamber can be discharged to the inflow duct. At an intermediate position the upper and lower further ports are out of register with the inflow port and the outflow port respectively.
The means to prevent direct flow between the inflow and outflow ducts may be a plug located in the tube. In the lower position of the chamber, leakage may occur from the chamber through the lower further port, between the chamber inside wall and the tube sidewall, through the outflow port and into the outflow duct. Similarly in the upper position, leakage may occur from the inflow duct, through the upper further port, between the chamber inside wall and the tube sidewall, through the outflow port into the outflow duct.
To obviate such leakage, the means preventing direct flow of liquid through the tube between the inflow and outflow ports may comprise reciprocable valve members, upper and lower valve seats being provided respectively at the upper end of the outflow duct and the lower end of the inflow duct. The valve members are carried by a valve carrier which is connected to the chamber for movement therewith. A coil spring accommodated in the valve carrier biases the valve members apart. In the lower position of the chamber, the valve member is unseated from the upper valve seat but the lower valve member seats on the lower valve seat to prevent leakage into the outflow duct. In the upper position the lower valve member is unseated from the upper valve seat but the upper valve member seats on the upper valve seat to prevent leakage from the inflow duct.
The presence of the ports is disadvantageous because the ports are not conducive to good flow of air or liquids. This is because:
(a) The valves open before the ports are fully in register thereby partly obstructing flow; PA1 (b) The escape of air bubbles from the top of the chamber is difficult since they excape via the ports which are approximately one third of the tube surface diameter; PA1 (c) The inflow of liquid into the chamber and escape of air from the chamber are confused because they both occur simultaneously using the same port which has only a small aperture, and air as small bubbles is present in the bottle and measuring device during rapid operation. PA1 (d) There is a tendency for air to remain locked, after filling, at the top of the chamber. This can lead to inaccurate measure. PA1 (e) If, as commonly occurs, the measuring device is fixed out of the vertical, there is a residue of liquid left at the bottom of the chamber and radially opposite the ports after draining, causing variation in measure. PA1 (f) The ports cause problems when handling liquids more viscous than drinkable distilled alcohols.
Also the engaging surfaces of the valve members and valve seats are flat and normal to the direction of movement of the valves i.e. the longitudinal direction of the flow tube. Thus the force which either valve member can exert on the corresponding valve seat is limited to the force exerted by the coil spring urging the valve members apart. Consequently the sealing contact between either valve member and the corresponding valve seat is limited in its effectiveness and leakage as described above may still occur.